Glucomannans (GMs) from diverse natural plants have great potentiality in enhancing the host immune system. The protective effects of three GMs on the intestinal mucosal immunity in colitis mice were investigated and compared in this study. The three GMs (KGM, AGP, and DOP) were obtained from Amorphophallus rivieri, Aloe vera, and Dendrobium officinale, respectively, having different weight-averaged molecular weights (Mw), acetyl group content, and molar ratios of mannose to glucose (M/G). The three fractions were administered with or without dextran sodium sulfate (DSS) containing drinking water. Macroscopic observations (health state, crypt depth, and bowel thickness of colon tissue) were conducted. Furthermore, related cytokines and mRNA expressions of TLRs were measured by ELISA and RT-qPCR, respectively. Results showed that the administration of the three GMs improved the health state of colitis mice, such as the recovery of body weight, and the increase of the immune organ index, crypt depth, bowel wall thickness, and total number of immune cells. The integrity of intestinal mucosa was maintained by the increased number of goblet cells and mucin protein production. Further studies showed that GMs kept the balance between pro- and anti-inflammatory cytokines and also regulated the expressions of TLR-2, TLR-4, TLR-6, and TLR-9. The above results suggested that GMs could attenuate the intestinal epithelial injury and regulate the intestinal mucosal immunity. Structural features including the M/G ratio, Mw, and the content of acetyl groups jointly influence the protective effects of GMs on the colitis mice.